If you use org.javers.core.diff.custom.CustomBigDecimalComparator with a null value you get an NPE

There should be a null check for setScale and possibly for aRounded.equals(bRounded); aswell.
Also minor issue
The comment in line 21 is missing the .class -> BigDecimal.class
JaversBuilder.javers().registerCustomComparator(new CustomBigDecimalComparator(2), BigDecimal).build();